BT has since called for a temporary halt on all new and existing applications from lawyers to obtain such customer data until a "test case" can be heard.

This so-called test case has been adjourned until 11 January 2011, which involves lawyers from Gallant Macmillan, who are attempting to obtain a court order to get the names and addresses of a "large number" of broadband users from PlusNet, BSkyB and Be Internet.

The case involves P2P users suspected of illegally downloading content from The Ministry of Sound.

Anti-piracy law firms such as ACS:Law and Grant Macmillan partner with rights holders and use software to track file-sharing sites which identifies the IP (internet protocol) of those users sharing copyrighted content.

The firms then apply for a court order to obtain the names and mailing addresses of the customers from their ISP. In most cases the lawyers then send the alleged copyright infringer a letter asking for a one-off fee or threatening court action if that fee is not paid.

BT's lawyers have requested more details on the security systems used to store customers data, following the ACS:Law data breach last month.

Data breach concerns

"The incident involving the ACS:Law data leak has further damaged people's confidence in the current process," a BT spokesman said.

"We want to ensure broadband subscribers are adequately protected so that rights holders can pursue their claims for copyright infringement without causing unnecessary worry to innocent people.

"We have not simply consented to these orders in the past, we have asked for stricter terms as public concern has risen. The data leak with ACS:Law prompted us to take further action today."

ACS:Law is now being investigated by the Solicitors Regulation Authority over the data leak.